ZIP-code–level distress as a predictor for advanced stage and mortality in female breast cancer across a multiethnic cohort in Hawaiʻi.

1649 Background: Native Hawaiian and Pacific Islander (NHPI) patients experience worse breast cancer outcomes; however, the role of neighborhood-level structural disadvantage remains underexplored. We evaluated whether the Distressed Communities Index (DCI), a ZIP-code–level socioeconomic measure, is associated with stage at diagnosis and survival in a multiethnic breast cancer cohort. Methods: We conducted a retrospective cohort study of 10,421 female patients with breast cancer treated at a major tertiary cancer center in Honolulu, Hawaiʻi (2000-2024). DCI was assigned by residential ZIP code using the Economic Innovation Group DCI (American Community Survey 5-year estimates, 2019–2023) and dichotomized as low (DCI 1–3) versus high (DCI 4–5). Patients missing ZIP code or stage at diagnosis were excluded. Associations with advanced stage (III/IV) were assessed using logistic regression. Overall survival (OS), defined as time from diagnosis to death from any cause or last follow-up, was evaluated using multivariable Cox regression, adjusting for age, race/ethnicity, insurance, tumor characteristics, and stage. Results: The cohort included 1,982 White, 6,206 Asian, 2,067 NHPI, and 166 patients of other races/ethnicities. Baseline DCI distribution differed by race/ethnicity and insurance: NHPI patients were more likely to reside in high-distress communities than non-NHPI patients (38.9% vs 29.3% OR 1.54, p<0.001), as were Medicaid/uninsured patients compared with privately insured patients (51.4% vs 27.8%; OR 2.76, p<0.001). Advanced stage at diagnosis was more frequent in high-DCI neighborhoods than low-DCI neighborhoods (10.0% vs 6.7%; p<0.001) and remained independently associated with high DCI after adjustment (aOR 1.29; p=0.021). Higher DCI was also associated with worse survival (aHR 1.16, 95% CI 1.07–1.27; p<0.001), demonstrating a dose-response pattern across DCI categories (p for trend <0.001). No significant interaction was observed between DCI and NHPI status (p=0.493). Median OS was 247 (234-260) months for White patients, 247 (241-253) months for Asian patients, 227 (215-239) months for NHPI patients (log-rank p<0.001). In multivariable analysis, NHPI patients had higher mortality than White patients (HR 1.27, 95% CI 1.12–1.43; p<0.001), while Asian patients had improved survival (HR 0.78, 95% CI 0.71–0.87; p<0.001). Medicaid/uninsured remained independently associated with higher mortality (HR 2.18, 95% CI 1.85–2.57; p<0.001). Conclusions: ZIP-code–level socioeconomic distress is independently associated with advanced stage at diagnosis and mortality in breast cancer and disproportionately affects NHPI and Medicaid/uninsured patients. DCI identifies communities at higher risk and provides a scalable, policy-relevant tool to support geographically targeted navigation, screening access, and resource allocation strategies.